Vocal communication and territoriality during the non-breeding season in a migrant warbler

The dry forest of Kalakad-Mundanthurai Tiger Reserve is an important habitat for wintering migrant birds. The most common migrant is the greenish leaf warbler, Phylloscopus trochiloides, Individuals defend territories, employing simple call notes to advertise territories, and more complex songs during prolonged negotiations of territory boundaries. Playback experiments using recorded calls suggest that individuals respond equally aggressively to territorial intrusions by neighbours as well as strangers, but neighbour recognition cannot be ruled out, Boundary negotiations appear to be costly, and songs may serve as an indicator of a bird's body condition. Vocalizations are important in establishment of territories, which is a prerequisite for over-winter survival. Vocal behaviour thus influences local population dynamics.